Twin rake mechanical classifier

ABSTRACT

Apparatus for separating settled solids from liquid medium including a pair of juxtapositioned tank means constructed to include an inclined bottom having upright wall means for defining an upwardly open cavity area capable of containing predetermined amounts of liquid suspended solids and operable to permit solids to settle to the inclined bottom. Rake means, including a rake assembly operatively associated with each of the tank means, is provided for raking the settled solids upwardly along the inclined bottom for discharge through an opening defined in the inclined bottom. The rake assemblies are controlled through successive cycles of orbital movement whereby the rake assemblies are advanced along a first predetermined path adjacent the inclined bottom for effecting movement of the settled solids, elevated and advanced in an opposite direction along a predetermined path and thereafter lowered to position adjacent the inclined bottom at the start of a second cycle of operation. The rake assemblies include support means which will support and control movement of the rake assemblies in successive cycles of operation whereby one of the rake assemblies is advanced along said first predetermined path in a discharging direction while said other rake assembly is advanced along said second predetermined path in an opposite direction.

[ Mar. 12, 1974 United States Patent [1 1 Chapman et al.

[ TWIN RAKE MECHANICAL CLASSIFIER [76] Inventors: William A. Chapman,3032 dium including a pair of juxtapositioned tank means constructed toinclude an inclined bottom having upright wall means for defininganupwardly open cavity Bethwood Ln., Lithonia, Ga. 30058; NelsonSeveringhaus, 213 G16 ml area capable of containing predeterminedamounts of Cir Decatur Ga 30032 liquid suspended 'solrds and operable topermit solids to settle to the inclined bottom. Rake means. includ-Sept. 9, 1971 [21] Appl. No.: 178,950

[22] Filed:

ing a rake assembly operatively associated with each of the tank means,is provided for raking the settled solids upwardly along the inclinedbottom for discharge through an opening defined in the inclined hot-[52] U.S. 210/322, 2lO/523 [51] Int. B0ld 21/18 [58] Field of SearchReferences Cited a predetermined path and UNITED STATES PATENTSthereafter lowered to position adjacent the inclined opposite directionalong bottom at the start of a second cycle of operation. The rakeassemblies include support means which will sup- ..2lO/523X 2l0/523 Xport and control movement of the rake assemblies in 210/523 X mmwm mm mmLhm m U 00mm DCSB 409 i 1 9999 1111 ///l 782 4337 2543 6 2 9799 9 112.]

successive cycles of operation whereby one of the rake assemblies isadvanced along said first predeter- Primary Examiner-Samih N. Zaharnamined path in a discharging direction while said other AssistantExaminerT. A. Granger rake assembly is advanced along said secondpredetermined path in an opposite direction.

Attorney, Agent, or Firm-Newton, Hopkins Ormsby 13 Claims, 9 DrawingFigures [57] ABSTRACT Apparatus for separating settled solids fromliquid me- PAIENIEMRIZ m4 3796315 INVENTORS: W/[ZMM ,4 (MAMA/v PAIENTEDMAR I 2 I974 SHEU 2 UF 5 PATENTED MR 1 2 m4 SHEET 3 [If 5 PATENTED MAR12 I974 SHEH E OF 5 PATENTED MR 1 2 I974 sum 5 or 5 FIG 9 1 TWIN- RAKEMECHANICAL CLASSIFIER BACKGROUND OF THE INVENTION This invention relatestoclassifier means to be used for separating settled solids from liquidmedium such as in ore dressing, sand preparation and sewage disposal forsizing and dewatering.

In the processing of material such as sand, the sand is suspended in aliquid medium and is conveyed along a suitable conduit means into asedimentation tank. After the sand has been received in thesedimentation tank, the sand is allowed to settle to the bottom and isadvanced or moved along the bottom by suitable rake means for dischargeinto collection means or deposited on suitable conveyor means fortransfer to a remote collection station.

In the processing of sewage, the liquid material containing solids ispumped or transferred along conduit means to sedimentation tanks. Afterthe sewage material has been received in the sediment tanks, the solidsare allowed to settle to the bottom and are then advanced or moved alongthe bottom for discharge through suitable openings. After the sewagematerial has been discharged through the openings, the solids are thenmoved to various other processing stations.

Still other types of classifiers which utilize sedimentation tanks andrake means for separating the settled solids therefrom include varioustypes of ore processing operations, wherein the ore is transferred froma collecting point in liquid suspension to a sedimentation tank meanswherein the ore is allowed to settle from the liquid and separatedtherefrom.

A number of attempts have been made to provide rake means operativelyassociated with sedimentation tanks for separating settled solids fromthe liquid medium. The prior art raking means are extremely complex,utilizing 'a number of power shafts, gears, cams and various othercontrol elements. These prior art classifiers are extremely costly tomanufacture and unreliable in performance, requiring considerablemaintenance.

SUMMARY OF THE INVENTION The above disadvantages of the prior art rakeclassifiers have been overcome by the present invention which basicallyincludes a pair of juxtapositioned sedimentation tank means each havinga rake assembly operatively associated therewith for a controlledmovement through successive orbital cycles of operation. Thesedimentation tank means includes an inclined bottom having a dischargeopening and the rake assemblies are moved in successive cycles ofoperation through their orbital path wherein the rake means are advancedin a first direction along a first predetermined path adjacent theinclined bottom during a first portion of a cycle of operation and areelevated above the inclined bottom and advanced in a second oppositedirection along a second predetermined path during an additional portionof a cycle of operation, with the cycle of operation being completed'bylowering the rake assembly to position adjacent the inclined bottom tobegin a second cycle of operation. During advancement of the rakeassemblies along the first predetermined path adjacent the inclinedbottom, settled solids located on the inclined bottom will be advancedupwardly therealong for discharge through the opening defined in theinclined bottom.

One important feature of the present invention resides in the supportand control means for the rake assemblies which will permit one of therake assemblies to be advanced along the first predetermined path whilethe other rake assembly is moved along the second predetermined path.

Another important feature of the present invention resides in thecontrolled movement of the rake assembly to produce an almostrectangular motion of the rakes, thus maintaining the pool agitation ata minimum to allow maximum settling and increased solids removablecapacity.

Another important feature of the present invention resides in thelocation of the eccentric drive mechanism relative to the rakeassemblies, wherein the eccentric drive is located for imparting araising and lowering of the rakes in a cycle of operation, such that thelowering of the rakes by the eccentric drive helps maintain the rakes incloseproximity to the inclined bottom during transfer of the material tothe discharge openings.

The mechanical rake classifier of the present invention is constructedof two sets of rake assemblies which are suspended in balance, thusminimizing power and bearing loads required to raise and lower theassemblies.

A primary object of this invention is to provide a twin rake classifierwhich is simple in construction, economical to manufacture and reliablein performance.

Still other objects and advantages of the details of construction willbecome apparent upon reading the following description of theillustrative embodiment, with reference to the attached drawings whereinlike reference numerals have been used to refer to like parts throughoutthe several figures, and wherein:

BRIEF DESCRIPTION OF THE FIGURES OF DRAWING FIG. l is a perspective viewof a twin rake classifier embodying the principles of the presentinvention;

FIG. 2 is an enlarged fragmentary top plan view of the twin rakeclassifiers shown in FIG. I;

. FIG. 3 is a vertical sectional view taken along line 33 of FIG. 2,with parts broken away for purpose of clarity;

FIG. 4 is an exploded perspective view of one of the support and controlelements used for controlling a rake assembly during orbital cycles ofoperation;

FIG. 5 is an enlarged fragmentary perspective view showing the motor anddrive control means for the twin rake classifier shown in FIG. 1;

FIG. 6 is a vertical sectional view taken longitudinally through amodified form of the twin rake classifier embodying the principles ofthe present invention, with parts omitted and parts broken away forpurpose of clarity;

FIG. 7 is a fragmentary elevational view taken along line 7-7 of FIG. 6;

FIG. 8 is an enlarged exploded perspective view showing the details ofconstruction of the linkage control assemblies utilized in the twin rakeclassifier modification of FIGS. 6 and 7; and,

FIG. 9 is a schematic plan view illustrating a further modification ofthe twin rake classifier tank means showing a flared side wall means.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT Referring now to thedrawings, the twin rake classifier embodying the principles of thepresent invention is generally represented by the reference numeral andwill be described with reference to sedimentation tank means 20, rakemeans 50, rake support and control means 100 and rake drive means 150.

The function of the sedimentation tank means is to provide a pair ofjuxtapositioned tank elements which will contain predetermined amountsof liquid suspended solids introduced therein by suitable conveyingmeans and which will allow the liquid suspended solids to settle to thebottom for separation from the liquid medium.

The function of the rake means 50 is to advance the settled solids alongthe bottom of the sedimentation tank means for discharge.

The function of the support and control means 100 is to provideeffective means for'supporting and controlling the rake means throughorbital cycles of operation for performing the settled solids separatingoperation.

The function of the drive means 150 is to drive the rake means throughsuccessive cycles of orbital movement whereby a continuous operation ofseparating settled solids from liquid medium can be performed.

As shown in FIGS. 1-3, the sedimentation tank means 20 include a bottommember 21. Bottom member 21 is supported in an inclined relationship, asshown in FIGS. 2 and 3 by a first-base support member 22 and a secondbase support member 23. Bottom 21 is provided with a pair of elongatedopenings 24, 25 located adjacent base support member 23. A pair ofupright sidewall members 26, 27 are provided along opposite lateral sideedges of the inclined bottom 21 and extend upwardly therefrom. Connectedbetween opposite ends of the sidewalls 26, 27 are a pair of end wallmembers 28, 29. The tank means 20 is divided into a pairofjuxtapositioned tanks 31, 32 by an intermediate upright wall member33. Wall member 33 extends from end wall 28 to end wall 29. The inclinedbottom 21 and upright wall members 26-29 will provide suitable means forcontaining predetermined amounts of liquid suspended solids. The liquidsuspended solids are introduced into the tank elements 31, 32 bysuitable conduit means (not shown).

As shown in FIGS. 1 and 3, an overflow opening 34 is provided in endwall 29. The overflow opening 34 is detailed in vertical location toallow liquid to flow outwardly therethrough prior to reaching anelevation which would permit the liquid to flow through the dischargeopenings 24, 25. A collection trough 35 is provided on the outsidesurface of end wall member 29 I and positioned for collecting andconveying liquid passing through the overflow opening 34. End wallmember 29 is provided with two openings 37, 38 located adjacentdischarge openings 24, 25, respectively. Openings 37, 38 are'detailed inlocation within end wall members 28 to provide a smooth surface forpermitting settled solids to be transferred along the inclined bottom21.

As shown in FIGS. 1-3, the rake means 50 includes a pair of rakeassemblies 51, 52. The rake assemblies 51, 52 are supported whereby rakeassembly 51 is in operative association with tank means 31 and rakeassembly 52 is in operative association with t'ank means 32. Each of therake assemblies 51, 52 are identical in construction and the componentparts of each 'of the rake assemblies will be described concurrentlywith the same reference numeral applying to like parts on both of therake assemblies. Each of the rake assemblies 51, 52 is constructed inthe form of elongated truss-shaped structural member which includes anupper support beam 53, a lower support beam 54, a number of verticalconnecting members 55, 56, 57 and a number of angle brace members 58,59. The structural members 53-59 are constructed of suitable metal stockmaterial with the connection points between the structured members beingmade by conventional welding means (not shown). The length of thetruss-shaped structural rake assemblies 50, 51 are detailed in length tobe slightly less than the elongated dimension of the tank means 31. 32,whereby the rake assemblies can be moved through oribital paths ofmovment within the tank means 31, 32, as will be described in moredetail hereinbelow.

As shown in FIGS. 1 and 3, a plurality of rake elements are secured tothe bottom edge of lower structural beam 54. Rake elements 60 areoriented in substantially right angular relationship relative tostructural member 54 and are detailed in dimensions to substantiallyfill the transverse dimensions between the sidewalls 26, 27 and theintermediate wall 33 whereby the rake elements 60 can effectively movesettled solids on the inclined bottom throughout the lateral width ofthe tank means 31, 32. The rake members 60 are equally spaced along thelongitudial axis of lower structural beam 54. As shown in FIGS. 1-3, therake assembly upper structural beam 53 includes a pair of support arms61, 62 extending from opposite ends thereof in substantiallylongitudinal alignment with structural beams 53. Support arms 61, 62 areconnected to structural beams 53 by suitably threaded connecting means63. The support arms 61, 62 are provided for supporting the rakeassemblies 51, 52 for movement through the orbital cycles of operation,as will be described in more detail hereinbelow.

Support arms 61, 62 are supported within opening (FIG. 4) provided-in anumber of guide members 101, 102, 103, and 1041. Guide members 101-104are connected to the upper surface of a pair of pulleyshaped supportelements 106, 107. Guide members 101 -10 1 are secured in positionrelative to the pulleyshaped support elements 106, 107 by suitablythreaded connecting means 108. Pulleys 106, 107 are constructed of anupper plate member 109, an intermediate plate member 110 and a lowerplate member 111. Plate members 109, 111' are of slightly largerdiameter than plate member 110 to provide an angular groove 112 definedtherearound for receiving a cable support member, as will be describedin more detail hereinbelow.

The plate members 109-111 are secured in position relative .to eachother by the threaded connecting bolts 108 which extend through threadedopenings provided in each of the plate members 109-111. Pulley shapedsupportelements 106, 107 are supported for pivotal movement about asubstantially vertical axis by an up standing pivot support member 118.Pivot support member 118 is inserted through an opening 113 in platemember 111, opening 114 in plate member 110, and the upper edge of thepivot support member 118 is in abutting contact with the lower surfaceof plate support member 109. Openings 113, 114 are detailed indimensions to rotatably receive pivot support member 118. Plate member109 is provided with an opening 115 which is much smaller in diameterthan the openings 113, 114 and will not permit the pivot support member118 to extend therethrough. The upper edge of pivot support member 118will be in abutting contact with support plate member 109 and will beretained thereon by conventional threaded connected means 117. Pivotsupport member 118 is secured to the upper surface of vertical frameelements 120. Frame elements 120 are secured to and extend from bottomwall 21 upwardly adjacent the outside surface of end walls 28, 29. Framemembers 120 are substantially coplanar aligned with the intermediatewall member 33.

As shown in FIGS. 3 and 4, the upper edge of'frames 120 are providedwith a pair of radially spaced rollers 121, 122. Rollers 121, 122 arecoaxially aligned relative to each other and provide a means forpivotally supporting pulley-shaped support elements 106, 107. The pivotsupport stud members 118 will support plate elements 106, 107 forpivotal movement about the vertical axis of the stud elements and thedimension of the stud elements are detailed relative to openings 113,114 to permit pivotal movement of the support elements 106, 107 about asubstantially horizontally aligned axis, with the rollers 121, 122providing a pivot support means for the horizontal axis. The horizontalaxes are coplanar aligned with the vertical axis of pivot stud members118.

The rake assemblies 51, 52 are supported by the .longitudinallyextending arms 61, 62 which extend through openings 105 defined inguides 101, 102. Rake assemblies 51, 52 are drivingly connected to thesupport elements 106, 107 by an endless cable 125. The endless cable 125is secured to the upper surface of upper structural beam members 53 by aplurality of conventional clamp elements 126. Endless cable 125 passesalong the upper surface of beams 53 and is fitted around annular grooves112 defined in support elements 106, 107. The connection of cable 125with the support elements 106, 107 will permit the rake assemblies 51,52 to transfer reciprocating movement of the rake assemblies intopivotal oscillating movement of the support elements 106, 107. The cablesuspension means 125 for the rake assemblies including clamp elements126 will permit readily removal of the rake assemblies for repair orreplacement of one rake element. The cable suspension means 125 willalso support the rake assembly whereby the rake assemblies will beadvanced in a substantially common plan during movement through theorbital cycles of operation.

Each of the rake assemblies 50, 51 including the support and controlmeans are suspended in balance, thus minimizing the power and bearingloads required to effect the continuous cycles of operation of the rakeassemblies.

As shown in FIGS. 1, 3 and 4, the pivot support elements 106, 107 arecontrolled for selected pivotal movement about the horizontal axis ofpivot support rollers 121, 122 by a cam control means which includes apair of cam elements 130, 131. Cams 130, 131 are attached to the bottomsurface of each of the pulleyshaped support elements 106, 107 bythreaded connecting members 132, which are inserted throughcomplementary openings within the plate members and threadably receivedby complementary threaded openings provided in cam elements 130, 131.Cam elements 130, 131 will effect displacement of the pulley-shapedsupport elements 106, 107 about the horizontal axis defined by rollers121, 122. Vertical displacement of cam elements 130, 131 is effected bymeans of a cam displacement lever 133. A cam displacement lever 1331soperatively associated with each of the cam elements 130, 131. Each ofthe cam displacement levers 133 includes an elongated link member 134pivotally attached at its lower end by a bracket member 135 to tankfloor 21. A cam engaging roller 136 is supported for rotation in theupper extended end of each of the link members 134 for contacting androtatably engaging cam elements 130, 131. The elongated link members 134extend through slots 137 provided in horizontal plate members 138. Platemembers 138 are supported-in vertically spaced relationship above floor21 by upstanding support brackets 139 and end walls 28, 29. Platemembers 138 are secured in a fixed position by conventional threadedconnecting members 141.

As shown in FlGS. 1 and 4, levers 134 are spring biased in a clockwisedirection by leaf springs 142. The leaf springs 142 are secured to theupper surface of plates 138 by a conventional threaded connecting member143. Adjustable limit stop plates 144 are attached to support plates138, on an opposite side of the cam displacement lever from leafsprings, and secured in selectively adjustable positions thereon byconventional threaded connecting means 145. The limit stop plates 144will permit selective adjustment of the extent of clockwise movement ofthe cam displacement support levers 134, to thereby control the timedrelationship of displacement of the cams 130, 131. Operational controlof the pulley-shaped support elements 106, 107 by the cam elements 130,131 will be described in more detail hereinbelow in the description ofoperation of the twin rake mechanical classifier.

The operationof the cams 130, 131 and the cam displacement members 133will control the movement of the rake assemblies in a cycle of operationwhich is almost rectangular in motion to give a minimum pool agitationthus allowing maximum settling and increased solid removal capacity.

The rake assemblies 51, 52 are driven through successive orbital cyclesof operation by a power motor means 150. Power motor means is supportedon a horizontal plate member 151. Plate member 151 is secured to theupper surface of intermediate wall member 33 adjacent end wall member28. Motor means 150 is secured to plate member 151 by conventionaladjustable connecting means (not shown).

As shown in FIG. 2, the motor means 150 includes a conventional poweroperable drive shaft 152. Shaft 152 supports a drive pulley 153 fordriving belt 154. At opposite end of belt 154 is in driving engagementwith pulley 155. Pulley 155 is fixed to a cross control shaft 157. Shaft157 is journaled for rotation in a pair of upstanding support brackets158, 159. Brackets 158, 159 are secured to the lateral side edges ofmotor support plate 151. Shaft 157 extends through the support brackets158,159 with the extended ends thereof drivingly supporting crankmembers 160, 161. Crank member 160 includes a radially displaced crankpin 162. Crank pin 162 is connected to one end of a pair of elongatedlink members 163, 164. Opposite ends of link '7 members 163, 164 areconnected by pin connecting means 165 to the upper beam 53 of rakeassembly 51. Rotary crank member 161 is provided-with a crank pin 166radially displaced from the axis of the crank member 161. As shown inFIG. 5, a pair of elongated driving link members 171, 172 are connectedadjacent one end to crank pin 166. Opposite ends of link members 171,172 are connected to a pivot connecting pin 173. Pin 173 is fixed to theupper support beam 53 of rake assembly 52.

As shown in FIG. 5, crank pins 162 and 166 are substantially 180radially displaced relative to the axis of the rotary crank members1611, 161. The radial displacement of crank pins 162, 166 will effect adriving movement of rake assembly 51 in one direction while driving rakeassembly 52 in an opposite direction and thereafter automaticallyreversing the direction of operations of the rake assemblies 51, 52.

The location of the crank members 160, 161 below the upper beam 53 ofthe rake assemblies will operate to pull the connecting links and rakemembers downwardly during one portion of the cycle of operation, toinsurethat the rake elements 1611 are maintained in close proximity tothe inclined bottom to provide maximum raking action of the rakingelements. The location of the crank members 1650, 161 will impart anupward movement of the rake assemblies during an additional portion ofthe cycle of operation to aid in lifting the rake assemblies to theupwardly displaced position.

A modified tank construction is shown in FIG. 9 wherein the side walls26a, 27a diverge outwardly away from discharge openings 24a, 25a andtoward end wall 290. The diverging walls 26a, 27a will increase thesedimentation area of the tank means without substantially increasingthe rake assembly construction. 1n using a diverging wall construction,the rake elements 611a will be gradually increased in length as theyapproach end wall 2%. Sufficient clearance is provided between therake'elements and the wall construction to permit the required cyclicoperation. The support for the rake assemblies adjacent end wall 29awould be slightly larger than the support adjacent end wall 28a. 4

. OPERATION In utilizing the twin rake classifier embodying theprinciples of the present invention, the classifier is supported in aposition substantially as shown in H6. 3 and a supply of liquidsuspended solids is introduced into each of the tank members 31, 32. Thesupply of liquid suspended solids is introduced by conventional conduitmeans (not shown). The amount of liquid suspended solids can begradually introduced or can be introduced at prescribed amounts. Excessliquid introduced into the tank means will overflow through openings 341into the collection trough 35. Solids contained within the tank members131, 132 will be allowed to settle to the inclined bottom surface 21.

In operation of the twin rake assemblies 51, 52, motor means 150 isenergized thereby effecting rotary movement ofcontrol shaft 157 throughthe pulley and belt drive means 153-155. Rotary movement of controlshaft 157 will effect movement of the rake assemblies 51, 52. Aclockwise rotation of control shaft 157 will effect movement of rakeassembly 52 rightward and at the same time will effect movement of therake assembly 51 leftward. Since the rake assemblies 51, 52 aresupported and frictionally engaged with the pulley support elements1116, 1117, movement of the rake assemblies 51, 52 will effectoscillating movement of pulleyshaped support members 1116, 107 about thevertical axes of pivot supports 118. An oscillating movement of thepulley-shaped support members 106, 1117 will also effect displacement ofcams 1311, 131. Referring now particularly to FIG. 3, displacement ofrake assembly 52 to the left will cause the pulley-shaped supportmembers 1116, 1117 to move clockwise (FIG. 2). A clockwise movement ofthe pulley-shaped support members 1116, 1117 will cause cam members 131to move to the left and contact cam displacement lever rollers 136. Ascams 131 contact rollers 136, the cams will effect a displacement of theelongated supported levers 134 until the levers contact the left edge ofslots 137. After levers contact the left edge of slots 137, the cam willthen advance over'rollers 136. Advancement of cams 131 over rollers 136will elevate the cams to thereby pivot the pulley-shaped support members106, 107 about the horizontal axis defined by guide rollers 121, 122.Pivotal displacement of the pulley-shaped support members 1116, 167about a horizontal axis will elevate rake assembly 52. The drivingdisplacement of the rotary crank pin 166 is detailed such that as soonas the rake assembly 52 has been elevated the crank pin will thenreverse direction of the rake assembly to move the rake assembly to theright, as shown in FIG. 3.

As soon as the cams 131 have been moved to a position above rollers 136,the leaf spring means 142 will effect movement of the rollers to theright until rollers 136 contact a stop member 131a located on the rightedge of cams 131. During displacement of the rake assembly 52, to theright by the rotary driving crank pin 166, the pulley shaped supportmembers 1116, 107 will be moved counterclockwise (FIG. 2). Cams 131 aredetailed in design to maintain rake assembly 52 in an elevated positionuntil the rake assembly 52 reaches the right most driven position bycrank pin 166. As soon as the driving crank pin 166 advances the rakeassembly 52 to the rightward limit position, as shown in FIG. 3, theelongated levers 134 supporting rollers 136 will contact the limit stopplate 144 to thereby prevent any further movement of rollers 136,allowing the cams 132 to be displaced therefrom, to permit the rakeassembly 52 to be lowered into position adjacent inclined bottom wall21. A continued rotation of rotary driven crank member 166, will thenadvance the rake assembly 52 to the left, with the rake elementssupported adjacent the inclined bottom wall 21. Movement of rakeelements 611 to the left while in position adjacent the inclined bottomwall 21, will effect displacement of settled solids to the left. Acontinued movement of rake assembly 52 to the leftmost driven positionby crank pinll66, will again effectengagement of cams 131 with rollers136 for vertical displacement of the supporting pulleys 1116, 1117 andrake assembly 52.. i

The above described-displacement of the rake assembly 52 will be driventhrough an orbital cycle of operation wherein the rake elements 611 areadvanced in a first predetermined path adjacent bottom wall 21 and in adirection toward discharge opening 25. After the rake assembly 52reaches the leftmost position, the cam displacement rollers 136 willelevate the rake element 60, and cams 131 will maintain the rakeelements 60 in an elevated position while advancement in a secondopposite direction along a second predetermined path substantiallyparallel to the first predetermined path and substantially parallel tothe inclined bottom wall 21.- During a completion of the orbital cycleof operation, cams 131 will operate to lower the rake-elements 60 intoposition again adjacent bottom wall 21. Motor drive means 150 iscontinuously driven and will effect successive cycles of orbitaloperation of rake assembly 52 to advance the settled solids along theinclined bottom 21 for discharge through opening 25.

Since the rake assembly51, operatively associated with tank means 31, isconnected and is driven simultaneously with rake assembly 52, thecontrol cams 130 will effect a corresponding control movement of rakeassembly 51 through sucessive orbital cycles of operation to therebyseparate the settled solids contained in tank 31, for discharge throughopening 24. Since the rake assemblies 51, 52 are drivingly connected atsubstantially 180 angularly displaced with drive control shaft 157, therake assembly 51 will be driven through one portion of an orbital cyclewhile the rake assembly 52 is being moved through an opposite portion ofthe orbital cycle of operation.

The rotary driven'crank pins 162, 166 are detailed in their drivingdisplacement for effecting advancement of the rake assemblies 51, 52along the first predetermined path from a position adjacent end wall 29to a displaced position adjacent end wall 28 and for return movementalong the second'predetermined path to a position adjacent end wall 29.

MODIFICATION OF THE RAKE ASSEMBLY SUPPORT AND CONTROL MEANS Referringnow particularly to FIGS. 6-8, a modified rake assembly support anddrive means is shown and generally represented by the reference numeral200. The modifications shown in FIGS. 6-8 include a sedimentation tankmeans 220 similar in construction to tank shown in FIGS. 1-5. Tank 220includes a bottom member 221 supported in an inclined relationship byfirst and second base support member 222, 223. Bottom 221 is providedwith a discharge opening means 224 adjacent base support member 223. Thetank means 220 includes a pair of upright sidewall members (not shown)provided along opposite lateral side edges of the inclined bottom 21 andextending upwardly therefrom. Connected between the opposite ends of thesidewalls are a pair of endwall members 228, 229. Tank means 220 isdivided into a pair ofjuxtapositioned tanks in the same manner asdescribed above in regard to tank 20 and includes an intermediate wallmember 230. Wall member 230 extends from endwall 228 to endwall 229.

As shown in FIG. 6, an overflow opening 231 is provided in endwall 228.Overflow opening 231 is detailed in vertical location to allow liquid toflow outwardly into a discharge trough means 232. Trough 232 is providedon the outside of endwall 228 and positioned for collecting andconveying overflow liquid passing through opening 231.

As shown in FIGS. 6 and 7, the sedimentation tank means 220 includes apair of rake assemblies 240, 241. The rake assemblies 240, 241 aresupported in operative association with the sedimentation tank means220. Each of the rake assemblies 240, 241 is similar to the rakeassemblies 56, 51 described hereinabove. Each of the rake assemblies isconstructed in the form of elongated truss-shaped structural memberhaving an upper support beam 243, a number of vertical extendingconnecting members 244 and a number of angle brace members 245. Aplurality of rake elements 246 is secured to the bottom edge of lowerstructural beam 243.

As shown in FIGS. 6 and 7, each of the rake assemblies 240, 241 includesa support bracket 247 extending vertically upward from opposite ends ofthe rake assemblies. The upper extended ends of the support brackets 247are provided with roller support members 248.

As shown in FIGS. 6 and 7, the rake assemblies 240, 241 are supportedadjacent their opposite ends by support assemblies 256, 251. Each of thesupport assemblies 250, 251 is secured in vertically orientedrelationship to the upper edge of the intermediate wall member 230. Thesupport assemblies 250, 251 are secured to the intermediate wall byconventional threaded connecting elements 253. Each of the supportassemblies includes a vertically extending support standard 254. Supportstandards 254 provide a pair of horizontally spaced coaxially alignedbearing members 255, 256. Bearing members 255, 256 provide means forpivotally supporting transverse support plates 257. The support plates257 include horizontally extending pivot members 258, 259 which arejournaled within the bearing members 255, 256, respectively. Oppositeends of the plates 257 are provide with coaxially aligned horizontallyextending pivot elements 260, 261. Pivot elements 260, 261 provide apivot support means for hanger brackets 265. Hanger brackets 265 are ofsubstantially U-shaped construction and include base 268 and a pair ofupstanding legs 266, 267. Base 268 privides a guide track means forsupporting rollers 248. A second track member 269 is secured betweenlegs 266, 267 in substantially parallel relationship relative to basemember 268 and defines therebetween a track for engaging and retainingthe support roller 248.

The above described support assemblies 250, 25] provide means forsupporting the support plate 257 for pivotal movement about the axis ofbearing members 255, 256 and the hanger brackets 255 provide track meansfor permitting rolling displacement of the rake assemblies. The pivotsupport members 260, 261 will permit the hanger brackets 265 to pivotrelative to the plate support member 257 whereby the hanger brackets aremaintained in a vertically oriented position. The track elements 268,269 are detailed in substantially parallel relationship relative to thetank bottom 221 whereby the rake assemblies 240, 241 can be moved inparallel relationship relative to the tank bottom in a cyclic operationfor advancing the settled particles of material outwardly through thedischarge opening 24, as will be described in more detail hereinbelow.

As shown in FIG. 6, the rake assemblies 240, 241 are driven in cycles ofraking movement relative to the support tracks 268, 269 by means of apower motor means 270. The power motor means 270 is supported aboveintermediate wall member 230 and includes a conventional gear box andpower drive shaft (not shown). Secured to opposite ends of the powerdrive shaft are a pair of rotary crank members 271 (only one of thecrank members has been shown in FIG. 6 however, it is to be understoodthat a second rotary crank member would be provided on an opposite sideof the drive shaft extending from the gear box). One of the cranks 271is connected by a driving link means 272 tothe rake assembly 240. Theopposite rotary crank 271 is connected by a driving link member 273 tothe rake assembly 241. The rotary crank members 271 are connected infixed angular offset relationship to the power drive shaft whereby thelink elements 272, 273 are 180 angular displaced relative to each other.The above described relationship will effect movement of one of the rakeassemblies in one direction while moving the other rake assembly in anopposite direction. The motor drive means 270 will effect continuouscycles of operation of the rake assemblies 240, 241 in a similar manneras described above in regard to the embodiment shown in FIGS. 1-5.

Vertical displacement of the rake assemblies 240, 241 from a positionadjacent the tank bottom 221 to an elevated position, is controlled by apair of linkage control assemblies 280,281 with one of the linkageassemblies being connected, respectively, to an intermediate portion ofeach of the rake assemblies 240, 241 and extend vertically above therake assemblies.

As shown in FIG. 8, each of the linkage assemblies includes a maincontrol link 283. The main control links 283 are connected in fixedrelationship relative to the rake assemblies 240, 241. The upperextended ends of the main control link 283 include elongated slot means284. Slot means 284 provides a support track for slidably supportingcontrol rollers 285. Rollers 285 are rotatably mounted on support shafts286. Support shafts 286 extend through the rollers 285, through theelongated slots 284, through a spacer element 287 and through firstmovable control links 288. The first movable control links 288 arepivotally connected adjacent their lower ends by pivot members 289-tosecond control links 290. Second control links 290 are pivotally securedby pivot elements 291 to a lower displaced portion of the main controllink 283. The pivot support members 286, 289, 291 are secured in anassembled relationship by conventional retaining means (not shown). Theupper extended ends of the second control links 290 are provided withlimit stop members 293. The limit stop members 293 will engage lateraledges of first control links 288 to limit the amount of counterclockwisemovement of first control links 288 and to limit the amount of clockwisemovement of second control links 290.

As shown in FIGS. 6 and 8, rollers 285 are supported in rollingengagement with apair of vertically spaced track elements 295, 296.Track elements 295, 296 are detailed in vertical spacing to define guidetrack means which will permit horizontal displacement of the rollers 285and rake assemblies 240, 241. The guide track elements 295, 296 aresecured at their opposite ends to a pair of horizontally extendingtransverse support frame elements 297, 298. The oppositely extended endsof the frame elements 297, 298 are secured to an intermediate portion ofthe sidewall members of the sedimentation tank means 220. The frameelements 297, 298 are supported in vertically spaced position above therake assemblies and detailed in location whereby the linkage assemblies280, 281 will extend upwardly through the frame elements 297, 298 withthe lateral space therebetween in detail to permit the required amountof reciprocating movement of the rake assemblies 240, 241 in slidablysupported by frame element 297 and are urged to the right as shown inFIG. 8 by a compression spring 300. Control elements 299 aredetailed inlocation to contact the control links 288, 290 when they are moved to anextreme left position, as shown in FIG. 6, to effect movement of thelinks to their extreme extended clockwise and counterclockwisedirections of movement until the limit stop members 293 contact controllink 288. A second control element 301 is slidably supported by theframe element 298 adjacent each of the linkage assemblies. Controlelement 301 is urged to the left as shown in FIG. 8, by compressionspring 302. The control element 301 .is detailed inlocation relative tolinkage assemblies 280, 281 whereby the control element 301 will contactcontrol links 288, 290 and effect movement of the control links to acollapsed position. I

Referring now particularly to FIG. 6, the rake assembly 240 is advancedto the right by a counterclockwise rotation of crank element 271.Movement of the rake assembly 240 to the right will effect displacementof roller 285 along the tracks 295, 296. Prior to movement of the crankelement 271 to an extreme rightward position, the linkage controlelements 288, 290 will contact the control element 301, which will pivotthe control links to a collapsed position, away from their extendedlimit position. As the links 288, 290 are moved to the collapsedposition, the roller support shaft 286 will be displaced downwardly tothe lower edge of guide slot 284. Movement of the shaft 286 downwardwithin slot 284 will permit an upward displacement of the rake assembly240. The above described movement of the linkage control assembly 280will be effected simultaneously with an opposite controlled movement ofthe linkage control assembly 281 to an extended position. Since the rakeassemblies 240, 241 are connected in 180 angularly ofiset drivingrelationship, the rake assembly 241 will be advanced to the leftsimultaneously with rightward movement of rake assembly 240. During aleftward displacement of the rake assembly 241, the control links 288,291 will be maintained in the collapsed position, as shown in FIG. 6. Acontinued leftward displacement of the rake assembly 241 will cause thecontrol links 288, 290 to contact the first control element 290. Acontinued leftward movement of the rake assembly 241 will cause controlelement 290 to move the control links 288, 291 to their extended limitposition. With the links 288, 291

in their extended limit position, the links will be longi- I tudinallyaligned relative to each other. As the links 288, 290 move to theirextended limit position, the roller support shaft 286 will be displacedupwardly in slot 284. An upward displacement of roller 285 will effect adownward displacement of the rake assembly 241 to move the rake assemblyinto position adjacent the inclined bottom 221.

The control elements 299, 301 for each of the linkage control assembliesare detailed in their location to contact and etfect movement of thelinkage control elements between their extended limit position and theircollapsed position such that the rake assembly 240 will move upward witha simultaneous downward displacement of rake assembly 241 and viceversa.

It now becomes apparent that the above described illustrative embodimentof a twin rake mechanical classifier is capable of obtaining the abovestated objects and advantages. It is obvious that those skilled in theart 13 may make modifications in the details of construction withoutdeparting from the spirit of the invention which is to be limited onlyby the scope of the appended claims.

What is claimed is: a

1. Apparatus for separating settled solids from liquid mediumcomprising, in combination:

a. a pair of juxtapositioned tank means, each of said tank meansincluding an inclined bottom with upright wall means for defining anupwardly open cavity area capable of containing predetermined amounts ofliquid suspended solids, wherein said solids are permitted to settle tosaid inclined bottom, and wherein an upper edge of said inclined bottomdefines an opening for permitting solid particles to be dischargedtherethrough;

b. a pair of rake assemblies, each rake assembly including a pluralityof rake elements supported thereon, and wherein one of said rakeassemblies is operatively associated with each of said tank means formoving-said settled solids along said inclined bottom for dischargethrough said opening in response to movement of said rake elements alonga-first predetermined path adjacent said inclined bottom and in a firstdirection toward said discharge opening;

means for supporting said rake assemblies for movement throughsuccessive cycles of operation wherein said rake elements are advancedalong said first predetermined path adjacent said inclined bottom ofeach of said tank means, with the rake elements moving in said firstdirection during a portion of a cycle of operation, said rake elementsbeing displaced above said inclined bottom and advanced in a secondopposite direction along a second predetermined path during anadditional portion of a cycle of operation and with said rake elementsbeing lowered to said position adjacent said inclined bottom during acompletion of a cycle of operation, said supporting means including asupport element oscillatably movable about a substantially verticallyoriented axis, with said rake assemblies being supported by said supportelement such that said rake elements are moved along said first andsecond paths of said cycle of operation during said oscillating movementof said support element, cam means operatively associated with saidsupport element for effecting movement of said support element about asubstantially horizontally oriented axis whereby said rake elements canbe displaced from said inclined bottom and can be lowered to positionadjacent said inclined bottom under control of said cam means duringportions of said cycle of operation; d. control means operativelyassociated with said rake assemblies for effecting movement of said rakeelements through successive cycles of operation whereby solid particlessettled to said inclined bottom can be advanced therealong anddischarged through said discharge opening; and said means for supportingsaid rake assemblies including a number of oscillatably operable supportelements longitudinally spaced along said rake assemblies for supportingand controlling said rake means through said orbital cycles ofoperation, each of said support elements including said cam means andsaid cam control element, and each support element being a pulley havingan annular groove;

2. Apparatus as in claim 1 wherein an endless cable is passed around thegrooves'of two of said pulleys and said rake assemblies are attached toand supported by said cable, whereby movement of the rake assembliesthrough their cycles will effect oscillation of said cables.

3. Apparatus as in claim 2 wherein the horizontal axes about which saidsupport elements are movable are provided by maintaining said elementson the upper horizontal edges of vertically positioned, plate-like framemembers, said edges having upstanding pins which provide said verticallyoriented axes, said support elements being provided-with openings inwhich said pins are received.

4. Apparatus as in claim 3 wherein said edges of said frame members areprovided with rollers on which said support elements rest, said rollersproviding the horizontal axes about which said support elements aremovable.

5. Apparatus for separating settled solids from liquid mediumcomprising, in combination:

a. a pair of juxtapositioned tank means, each of said tank meansincluding an inclined bottom with upright wall means for defining anupwardly open cavity area capable of containing predetermined amounts ofliquid suspended solids, wherein said solids are permitted to settle tosaid inclined bottom, and wherein an upper edge of said inclined bottomdefines an opening for permitting solid particles to be dischargedtherethrough;

b. a pair of rake assemblies, each rake assembly including a pluralityof rake elements supported thereon, and wherein one of said rakeassemblies is operatively associated with each of said tank means formoving said settled solids along said inclined bottom for dischargethrough said opening in response to movement of said rake elements alonga first predetermined path adjacent said inclined bottom and in a firstdirection toward said discharge opening;

c. means for supporting said rake assemblies for movement throughsuccessive cycles of operation wherein said rake elements are advancedalong said first predetermined path adjacent said inclined bottom ofeach of said tank means, with the rake elements moving in said firstdirection during a portion of a cycle of operation, said rake elementsbeing displaced above said inclined bottom and advanced in a secondopposite direction along a second predetermined path during anadditional portion of a cycle of operation and with said rake elementsbeing lowered to said position adjacent said inclined bottom during acompletion of a cycle of operation, said supporting means including asup- 1 port element oscillatably movable about a substantiallyvertically oriented axis, with said rake assemblies being supported bysaid support element such that said rake elements are moved along saidfirst and second paths of said cycle of operation during saidosciallating movement of said support element, cam means operativelyassociated with said support element for effecting movement of saidsupport element about a substantially horizontally oriented axis wherebysaid rake elements can be displaced from said inclined bottom and can belowered to position adjacent said inclined bottom under control of saidcam means during portions of said cycle of operation;

d. control means operatively associated with said rake assemblies foreffecting movement of said rake elements through successivecycles ofoperation whereby solid particles settled to said inclined bottom can beadvanced therealong and discharged through said discharge opening; and

c. said support element extending on opposite sides of said verticallyoriented axis and said rake assemblies being supported on said supportelement on opposite sides of said vertically oriented axis respectively,and said horizontally oriented axis intersecting said verticallyoriented axis and extending substantially parallel to the paths ofmovement of said rake assemblies.

6. Apparatus for separating settled solids from liquid medium as definedin claim further characterized in that said tank means includesoutwardly diverging sidewall means extending away from said dischargeopening whereby said diverging sidewall means will increase the capacityof the sedimentation area of said tank means to furnish maximum settlingcapacity with minimum amount of raking mechanism.

7. Apparatus for separating settled solids from liquid medium as definedin claim 5 further characterized in that said rake means and said rakesupport means are detailed in construction such that said rake means aresuspended in balance, thus minimizing the power and bearing loadsrequired.

8. Apparatus for separating settled solids from liquid medium asdescribed in claim 5 further characterized in that a control element isoperatively associated with said cam means and said oscillatablyoperable support element for effecting vertical displacement of saidsupport element about said substantially horizontally oriented axis, andwherein said cam means and cam control element are supported foryielding displacement relative to each other in the directions ofoscillatory movement of said support element about said substantiallyvertically oriented axis.

9. Apparatus for separating settled solids from liquid medium as definedin claim 8 further characterized in that said cam control element issupported for pivotal movement about a horizontal axis radially disposedrelative to said substantially vertically oriented axis of said supportelement, and wherein limit stop means is operatively associated withsaid pivotal support element for limiting the pivotal movement of saidpivotal support element in opposite directions about said radiallydisposed axis, with yielding means for biasing said support elementagainst at least one of said limit stop means.

10. Apparatus for separating settled solids from liquid medium asdefined in claim 9 further characterized in that said limit stop meansis selectively adjustable for varying the amount of said pivotalmovement of said control element.

11. Apparatus as in claim 5 wherein said support element is a pulleyhaving an annular groove and said rake assemblies are supported by anendless cable passing through said groove.

12. Apparatus as in claim 5 including cam means operatively associatedwith said support element for overbalancing said rake assemblies inrelatively opposite directions at the opposite ends of the strokes ofsaid rake assemblies.

13. A twin-rake apparatus for separating settled solids from liquidmedium comprising in combination a pair of side-by-side settling tankseach having a bottom wall inclining upwardly in the same longitudinaldirection in each tank, a pair of similar rake assemblies one associatedwith each of said tanks, a pair of pulleys mounted on vertical axes, oneat each end of said tanks, an endless cable passing around said pulleyswith one runof the cable lying above each rake assembly, means forsupporting each rake assembly on the corresponding run of the cable,means for imparting an oscillatory movement to said end pulleys wherebysaid rake assemblies will be given a reciprocatory movement in saidtanks, means for supporting said pulleys for tilting movement about ahorizontal axis located centrally between and parallel to the runs ofthe cable, and cam means responsive to oscillation of the pulleys foralternately raising one run of the cable and lowering the other and thenlowering said one run and elevating said other run, the arrangementbeing such that each rake assembly will be lowered when it moves towardthe upper end of said inclined bottom wall and raised when it movestoward the lower end thereof.

1. Apparatus for separating settled solids from liquid mediumcomprising, in combination: a. a pair of juxtapositioned tank means,each of said tank means including an inclined bottom with upright wallmeans for defining an upwardly open cavity area capable of containingpredetermined amounts of liquid suspended solids, wherein said solidsare permitted to settle to said inclined bottom, and wherein an upperedge of said inclined bottom defines an opening for permitting solidparticles to be discharged therethrough; b. a pair of rake assemblies,each rake assembly including a plurality of rake elements supportedthereon, and wherein one of said rake assemblies is operativelyassociated with each of said tank means for moving said settled solidsalong said inclined bottom for discharge through said opening inresponse to movement of said rake elements along a first predeterminedpath adjacent said inclined bottom and in a first direction toward saiddischarge opening; c. means for supporting said rake assemblies formovement through successive cycles of operation wherein said rakeelements are advanced along said first predetermined path adjacent saidincLined bottom of each of said tank means, with the rake elementsmoving in said first direction during a portion of a cycle of operation,said rake elements being displaced above said inclined bottom andadvanced in a second opposite direction along a second predeterminedpath during an additional portion of a cycle of operation and with saidrake elements being lowered to said position adjacent said inclinedbottom during a completion of a cycle of operation, said supportingmeans including a support element oscillatably movable about asubstantially vertically oriented axis, with said rake assemblies beingsupported by said support element such that said rake elements are movedalong said first and second paths of said cycle of operation during saidoscillating movement of said support element, cam means operativelyassociated with said support element for effecting movement of saidsupport element about a substantially horizontally oriented axis wherebysaid rake elements can be displaced from said inclined bottom and can belowered to position adjacent said inclined bottom under control of saidcam means during portions of said cycle of operation; d. control meansoperatively associated with said rake assemblies for effecting movementof said rake elements through successive cycles of operation wherebysolid particles settled to said inclined bottom can be advancedtherealong and discharged through said discharge opening; and e. saidmeans for supporting said rake assemblies including a number ofoscillatably operable support elements longitudinally spaced along saidrake assemblies for supporting and controlling said rake means throughsaid orbital cycles of operation, each of said support elementsincluding said cam means and said cam control element, and each supportelement being a pulley having an annular groove.
 2. Apparatus as inclaim 1 wherein an endless cable is passed around the grooves of two ofsaid pulleys and said rake assemblies are attached to and supported bysaid cable, whereby movement of the rake assemblies through their cycleswill effect oscillation of said cables.
 3. Apparatus as in claim 2wherein the horizontal axes about which said support elements aremovable are provided by maintaining said elements on the upperhorizontal edges of vertically positioned, plate-like frame members,said edges having upstanding pins which provide said vertically orientedaxes, said support elements being provided with openings in which saidpins are received.
 4. Apparatus as in claim 3 wherein said edges of saidframe members are provided with rollers on which said support elementsrest, said rollers providing the horizontal axes about which saidsupport elements are movable.
 5. Apparatus for separating settled solidsfrom liquid medium comprising, in combination: a. a pair ofjuxtapositioned tank means, each of said tank means including aninclined bottom with upright wall means for defining an upwardly opencavity area capable of containing predetermined amounts of liquidsuspended solids, wherein said solids are permitted to settle to saidinclined bottom, and wherein an upper edge of said inclined bottomdefines an opening for permitting solid particles to be dischargedtherethrough; b. a pair of rake assemblies, each rake assembly includinga plurality of rake elements supported thereon, and wherein one of saidrake assemblies is operatively associated with each of said tank meansfor moving said settled solids along said inclined bottom for dischargethrough said opening in response to movement of said rake elements alonga first predetermined path adjacent said inclined bottom and in a firstdirection toward said discharge opening; c. means for supporting saidrake assemblies for movement through successive cycles of operationwherein said rake elements are advanced along said first predeterminedpath adjacent said inclined bottom of each of said tank means, with therake elements moving in said first direction dUring a portion of a cycleof operation, said rake elements being displaced above said inclinedbottom and advanced in a second opposite direction along a secondpredetermined path during an additional portion of a cycle of operationand with said rake elements being lowered to said position adjacent saidinclined bottom during a completion of a cycle of operation, saidsupporting means including a support element oscillatably movable abouta substantially vertically oriented axis, with said rake assembliesbeing supported by said support element such that said rake elements aremoved along said first and second paths of said cycle of operationduring said osciallating movement of said support element, cam meansoperatively associated with said support element for effecting movementof said support element about a substantially horizontally oriented axiswhereby said rake elements can be displaced from said inclined bottomand can be lowered to position adjacent said inclined bottom undercontrol of said cam means during portions of said cycle of operation; d.control means operatively associated with said rake assemblies foreffecting movement of said rake elements through successive cycles ofoperation whereby solid particles settled to said inclined bottom can beadvanced therealong and discharged through said discharge opening; ande. said support element extending on opposite sides of said verticallyoriented axis and said rake assemblies being supported on said supportelement on opposite sides of said vertically oriented axis respectively,and said horizontally oriented axis intersecting said verticallyoriented axis and extending substantially parallel to the paths ofmovement of said rake assemblies.
 6. Apparatus for separating settledsolids from liquid medium as defined in claim 5 further characterized inthat said tank means includes outwardly diverging sidewall meansextending away from said discharge opening whereby said divergingsidewall means will increase the capacity of the sedimentation area ofsaid tank means to furnish maximum settling capacity with minimum amountof raking mechanism.
 7. Apparatus for separating settled solids fromliquid medium as defined in claim 5 further characterized in that saidrake means and said rake support means are detailed in construction suchthat said rake means are suspended in balance, thus minimizing the powerand bearing loads required.
 8. Apparatus for separating settled solidsfrom liquid medium as described in claim 5 further characterized in thata control element is operatively associated with said cam means and saidoscillatably operable support element for effecting verticaldisplacement of said support element about said substantiallyhorizontally oriented axis, and wherein said cam means and cam controlelement are supported for yielding displacement relative to each otherin the directions of oscillatory movement of said support element aboutsaid substantially vertically oriented axis.
 9. Apparatus for separatingsettled solids from liquid medium as defined in claim 8 furthercharacterized in that said cam control element is supported for pivotalmovement about a horizontal axis radially disposed relative to saidsubstantially vertically oriented axis of said support element, andwherein limit stop means is operatively associated with said pivotalsupport element for limiting the pivotal movement of said pivotalsupport element in opposite directions about said radially disposedaxis, with yielding means for biasing said support element against atleast one of said limit stop means.
 10. Apparatus for separating settledsolids from liquid medium as defined in claim 9 further characterized inthat said limit stop means is selectively adjustable for varying theamount of said pivotal movement of said control element.
 11. Apparatusas in claim 5 wherein said support element is a pulley having an annulargroove and said rake assemblies are supported by an endless cablepAssing through said groove.
 12. Apparatus as in claim 5 including cammeans operatively associated with said support element forover-balancing said rake assemblies in relatively opposite directions atthe opposite ends of the strokes of said rake assemblies.
 13. Atwin-rake apparatus for separating settled solids from liquid mediumcomprising in combination a pair of side-by-side settling tanks eachhaving a bottom wall inclining upwardly in the same longitudinaldirection in each tank, a pair of similar rake assemblies one associatedwith each of said tanks, a pair of pulleys mounted on vertical axes, oneat each end of said tanks, an endless cable passing around said pulleyswith one run of the cable lying above each rake assembly, means forsupporting each rake assembly on the corresponding run of the cable,means for imparting an oscillatory movement to said end pulleys wherebysaid rake assemblies will be given a reciprocatory movement in saidtanks, means for supporting said pulleys for tilting movement about ahorizontal axis located centrally between and parallel to the runs ofthe cable, and cam means responsive to oscillation of the pulleys foralternately raising one run of the cable and lowering the other and thenlowering said one run and elevating said other run, the arrangementbeing such that each rake assembly will be lowered when it moves towardthe upper end of said inclined bottom wall and raised when it movestoward the lower end thereof.